TREE ROOT DAMAGE
Why does this topic matter?
When does damage happen?
- The survival of urban trees depends critically on the health
of the roots.
- Roots and shoots are linked through a kind of circulatory
system: what hurts the one, hurts the other.
- Roots supply water and nutrients to the shoots, and get back sugar
and other compounds they need to grow and survive.
- Roots also store food, synthesize needed compounds, and provide
- Most tree roots lie in the top 6-18" of the soil, and usually
extend well beyond the canopy edge. About 1 of every 5 species (e.g.,
red oak) typically has a "heartroot" structure, with roots going deeper.
Very few species are actually taprooted. The actual root structure
of a particular tree is highly influenced by local site conditions.
- When something
cuts the roots, stops them from growing, or prevents them from breathing,
it causes damage and threatens the life of the tree.
- Common urban activities that often damage roots
- building construction
- road widening
- utilities repair
- sidewalk replacement
- lawn parking
- patio or paving installation
- grade change
- stockpiling materials on the ground
- Damage to the root system can often be detected from discoloration,
reduced size, or death of part or all of the tree’s crown.
Root damage on red oak leading
to stem failure
How do these acts hurt the tree?
How can the roots be protected?
- Loss of support. When the big buttress roots are cut
close to the tree, the tree has no support on that side and is prone to
- Loss of water. Cutting the roots that supply water
makes the tree vulnerable to drought, and also to pests that attack water-stressed
- Loss of nutrients. Roots must grow to take up many
nutrients, and when the soil is compacted by traffic or other loads,
roots are unable to penetrate it.
- Loss of food. Roots, like people, must be able to breathe
to use the food they get from the leaves. When roots are smothered, they
die from starvation.
Where can I get more information?
- Fence off the ground underneath the tree’s crown before
construction begins. If traffic must go through that area, first put down
6-12" of gravel or coarse mulch.
- Work with your utility company to tunnel under tree roots, when
- When replacing sidewalks, lay them around (or up and over) the
roots of older trees.
- Don’t raise the soil grade over roots more than a few inches without
- Set paving blocks in sand, and don’t mortar them together.
- Mulch wide and 2-6" deep, especially younger trees trying to establish
ISA. 1999. "Avoiding Tree Damage
During Construction" Champaign IL: International Society of Arboriculture.
For other information, advice and help on this topic, call offices of your
State Urban Forestry Coordinator or University Extension service, or visit
urban forestry websites.